CachyOS Hello is only one application that incorrectly interpret settings from KDE and shows shadows around window

1. Please answer, why don't you use Qt in there?
2. Please resolve the problem.
3. I don't think the issue is in the GTK, because all other applications used settings correctly and do not show shadows.

Start by reproducing the KDE settings and window-shadow behavior in CachyOS Hello, comparing it with other applications that handle the settings correctly. No source file or test is named; done means identifying the affected desktop integration and correcting the behavior so the application no longer shows incorrect shadows.

Written by the indexing model from the issue text.